In this basic Macromedia Flash animation tutorial you will see how to make a ball bounce and an animated shadow for it.

1.
Start by making a ball, we dont want a flat circle so we will make a gradient for it.
With the oval tool draw a circle on the stage, then make a filling gradient as the one shown below.
Also make a black stroke for the shape.

2.
Now place the ball at the top of the stage.
Right click the ball and choose convert to symbol, and then convert it to a movie clip.

3.
In the timeline name the layer ball, and make a new layer beneath it and name that shadow.
Now on the ball layer right click the timeline at frame 10 and choose insert keyframe.

4.
Right click at frame 5 and choose insert keyframe there to.
Now select frame 5 and drag the ball down to almost bottom, (make room for the shadow).

5.
In the timeline right click between frame 1 and 5 and choose create motion tween, then do the same between frame 5 and 10.

6.
Now the ball is jumping, and we only need to add the shadow.

7.
Now select the shadow layer, and with the oval tool draw the shadow as shown below.
Make sure the shadow shape is placed the same place as where the ball is going to at frame 5.

8.
Select the shadow and go to the filter panel, give it settings as in the image below.

9.
Insert a keyframe for the shadow layer at frame 10.
Then insert a keyframe at frame 5 also.
Right click between the keyframes and choose create motion tween.

9.
Now select frame 5 for the shadow layer, and select the shadow shape, go back to filter and set it as shown below.
Also use the transform tool on the shape to make it a bit smaller.

Now try to run your animation, and you will see as the ball bounces the shadow will get smaller and not so blurry, as it would in real life.